Polyurethane concrete slab sealer



1957 J. B. FITZGIBBON POLYURETHANE CONCRETE SLAB SEALER Filed April 29, 1953 H T TO RNE Y6 United States Patent 3,334,557 POLYURETHANE ONCRETE SLAB SEALER James B. Fitzgihhon, Burlington, Iowa, assignor to Phelan- Faust Paint Manufacturing Company, St. Louis, Mo., a corporation of Missouri Filed Apr. 29, 1965, Ser. No. 451,799 7 Claims. (CI. 94-13) This invention relates to improvements for slab sealers employed in expansion joints in concrete highways, and, in particular, relates to the use of polyurethane formed in situ in the crack or joint between adjacent slabs of concrete or other abutting slabs which are subject to adjacent expansion.

In the past there have been provided various types of calking or sealing compounds for the expansion joint between adjacent concrete slabs used in highways and the like. The joints may be between adjacent concrete slabs, as will be conventionally seen on the highway, or it can be a joint adjacent to a bridge or other joints used in the bridge structure. It is, of course, well known that it is very desirable to accommodate expansion of the slabs to prevent their buckling or pushing of part of a bridge structure off of its supports. The slab sealer or expansion joint is used to minimize the eflects caused by thermal expansion and contraction, and other forces such as expansion by forces exerted from dirt entrapment, water freezing in cracks, and the natural expansion of curing concrete, which can lead to the build up of very undesirable stresses within the highway concrete slabs forming the highway ribbon. If expansion is not provided for in the expansion joints, there can result blow-ups or cracking of the concrete pavement, and forcing of bridges off their supports.

Current methods employed in making expansion joints are, for example, to saw a slot in the roadway using a diamond tipped blade and fill this slot with a bituminous material that is preformed to fit. The purpose of this joint is to absorb the forces in the concrete and not to transmit them to the adjoining slabs of pavement or to adjoining bridges. This asphaltic based material has drawbacks due to very high compressive strengths in the range of 12004500 p.s.i., while forces necessary to move section of highway or bridges are in the range of only about 200 p.s.i. or less. Another property is that being preformed the bituminous material cannot fit into the slot exactly and therefore is subject to open spaces which fill with foreign matter, such as dirt, small rocks, water, which freezes in cold weather, and the like. These materials can and do transmit forces, and in the case of water freezing there are developed forces tending to loosen the joint due to cycles of expansion and contraction. Another disadvantage of bituminous materials is that they are not flexible and, during normal expansion and contraction cycles of heating and cooling, thus cause the opening of cracks which are subject to filling with foreign material and the transmission of forces, as pointed out previously. The use of preformed polyurethane slabs are also subject to many difliculties caused as pointed out above, which are inherent in the employment of the bituminous materials and other preformed slab sealers.

By means of the instant invention there has been provided a concrete slab sealer through the use of polyurethane formed in situ. By forming the slab sealer in situ by laying it down in liquid form and then permitting it to cure to a substantially solid material, a firm bond or adherence to the concrete by the slab sealer is provided to completely seal the adjacent portions of the abutting slabs to prevent the entrance of any water or foreign debris into the crack. Further, a good degree of compressibility and elasticity is provided through the use of the in situ formed polyurethane slab sealer of this invention to permit contraction and expansion of an adjacent concrete slab or variation of the size of the crack or joint in which the slab sealer is filled. In the employment of the in situ formed polyurethane slab sealer, the slot is filled with one or more plastic materials that will polymerize and expand, completely filling the slot and forming a joint that has none of the failures that are inherent as discussed above in the present types of materials employed. The slab sealer may be used as a single type of polyurethane, or, more preferably, it may be employed in the form of a low density rigid polyurethane of about 2 to 10 pounds per cubic foot density at the bottom of the crack, topped by a higher density of about 10 to 30 pounds per cubic foot elastomeric or flexible polyurethane, which has a highly improved degree of abrasion resistance and resilience.

As a further feature of the invention, the slab sealer may be very simply laid down at the site in liquid form and varying sizes of joints or cracks may be filled without the requirement of pre-shaping a solid joint and then fitting it to the crack. Thus, the slab sealer may be employed very advantageously at the site, without the requirement of highly developed or complicated controls.

The longevity and greatly improved.

The above features are objects of this invention and further objects will appear in the detailed description which follows and will be otherwise apparent to those skilled in the art.

For the purpose of example, there are shown in the accompanying drawings two forms of the slab sealer of this invention. It is to be understood that these drawings are, however, for the purpose of example only and that the invention is not limited thereto.

In the drawings:

FIGURE 1 is a view in section of a slab sealer using only a single type of polyurethane which is of medium density; and

FIGURE 2 is a view in cross-section of abutting slabs of concrete filled with the preferred slab sealer of this invention employing a relatively low density rigid polyurethane foam at the bottom of the crack topped by a relatively high density elastomeric or flexible polyurethane at the top.

In the employment of the materials providing the polyurethane slab sealer of this invention, it will be understood that various forms may be employed, as will be well understood in the art. Thus, the expansion joint or crack between adjacent slabs may be provided with a form at the top of the crack to provide a suitable retainmg device and properly vented to assure: the entire filling of the void up to the desired level. The plastic polyurethane liquid materials are introduced into the joint as liquids and level themselves out in the crack. Generally, after a period of thirty seconds or so, the liquid material begins to expand its volume and, after a period of three ruggedness of the slab sealer is further of about one hour is pro- I liquid polyurethane components to insure complete setting, after which period of time the slab is ready for highway tralfic. Generally, where the crack or joint between adjacent slabs is filled with this material, it is desired that for either the single polyurethane or the two-system polyurethane of low density and high density materials employed that they be filled up to not quite the top of the slot, i.e., within one-quarter to one-half inch of the top of the adjacent pavement slabs to prevent any protrusion that might tend to wear down or weaken the slab sealer.

The polyurethane slab sealer when formed in situ by this invention is free from the drawbacks inherent in the other systems as described above. The slab sealers, when applied, offer an entire joint filled with a favorable degree of flexibility and low compressive strength in the order of 75 p.s.i., coupled with toughness, water resistance, and an extremely firm bond to the concrete.

The polyurethane slab sealer of this invention has a number of desirable physical properties that lends itself very advantageously to use as an expansion joint or slab sealer for concrete or the like. Thus, the slab sealer has a relatively low compressive strength and is compressible under test conditions to in the order of one-half its thickness at 75 p.s.i. Further, the flexible or elastomeric slab sealer components can recover up to at least 90% of its original width when pressure is released. Further, it retains its flexibility at -40 F. and is stable at 150 F. The material is not sticky and does not accept foreign material from the surface of the highway, and rejects stones, sticks, and the like, that might have a tendency to become embedded and work into the surface because of traffic action. Further, the slab sealer is chemically inert and does not react adversely to petroleum or bituminous products or calcium or sodium chloride, which materials are normally found on highway surfaces. Additionally, the material, of course, gives or yields with the movement of the concrete through expansion and contraction cycles while retaining a very firm adherence or bond to the adjacent slabs to provide a very good seal and act as a block or seal and resist any water penetration. Additionally, the polyurethane material can be laid down very quickly and can be opened to vehicle traffic within a one hour period of time, and provides a long life. Lastly, the material can be laid down at the site by highway workers without any complicated fitting or cutting procedure required.

It will be well understood that the expansion joints to be filled by the polyurethane slab sealer of this invention can be of varying sizes. Also, it will be well understood that the slab sealer can be used between abutting concrete pavement slabs with a space in between the ends, whereby the slabs form part of the highway ribbon, or the slabs may be employed on bridge approaches and the like. Generally the expansion joint can be used wherever expansion and contraction are provided through the expansion space forming the expansion joint that is conventionally provided in the highway art. The joint, of course, as previously mentioned, can be of varying sizes, such as 4" wide, deep, and as long as the width of the highway ribbon, which may be anywhere from 10 to or the like. The forms that may be employed are conventional board forms to contain the liquid polyurethane, and the form at the top also may obviously be a flat board with holes drilled in it to provide for expansion in venting of the expansion joint space, and to provide for relief thr'ough any excess expansion or escape of gases and the like.

In the preparation of the joint before laying down the liquid polyurethane materials, it is desirable to remove sand and dirt from the sides of the abutting concrete slab to improve adherence to the polyurethane to the sides. No other special preparation is, however, required. In the actual laying down of the material, this can be accomplished in increments, as by laying down a fairly thin layer of the rigid foam at the bottom and allowing a few minutes before the next layer is laid down to build it up in size.

Where a single type of polyurethane foam is employed this can be of medium density, such as in the order of 10 pounds per cubic foot. Where employed, it should be laid down in the expansion joint to fill up to within onequarter inch or one-half inch of the top of the adjacent pavement surfaces. This material is not quite as abrasion resistant as the higher density elastomeric polyurethane material used as the top layer in the two-step type of sealer, and, as a result, it should not quite come up to the surface where contact by automobile tires and the like would tend to Wear it down. Where heavy traffic is encountered, the two-step polyurethane system is preferred.

The compressibility of the polyurethane material varies with its density. It has been found that the two pounds per cubic foot rigid polyurethane foam compresses to one-half its thickness at about 35 pounds per square inch, while the 4 pound foam compresses to one-half its thickness at about 70 to 80 p.s.i., and the six pound rigid foam compresses to about one-half its thickness and 123 p.s.i. The 10 pound per cubic foot flexible foam compresses to one-half its thickness at about 23 p.s.i., while the 25 pound per cubic foot flexible foam compresses to about onehalf its thickness at 124 p.s.i. Where the two-step system is employed, the bonding together of the low density rigid polyurethane foam and the higher density elastomeric or flexible polyurethane foam is very good, and, accordingly, breaking away or wearing away of the top high density flexible polyurethane foam is avoided or substantially minimized. To increase the adherence or bonding of the two types of polyurethane foam, it has been found desirable to approximate the compressive strengths employed in the low density and high density polyurethane foam, so that their compressive strength is of the same order. A rigid foam of four pounds per cubic foot and a flexible foam or 15 pounds per cubic foot have been found to be desirable in this respect as they both approximate lbs. p.s.i. compressive strength.

The slab sealers of this invention have shown very good recovery after compressive tests where they have been compressed to one-half of their original thickness as described above. This recovery is of the order of upward of 99%, as an example 99.7%, for 18 pound flexible foam and for 10 pound per cubic foot flexible foam. Further, the high density flexible foam has a hard glaze surface that works very well to provide abrasion resistance and minimize scuffing or embedding of foreign materials.

The manufacture of polyurethane foams is well known in the art and this invention merely employs conventional polyurethane compositions which may be of varying densities. The foamed polyurethanes are conventionally prepared by reacting various polyols with various types of isocyanates, such as diisocyanate or tri-isocyanate. The cellular structure employed in the foam may be obtained by using an excess of isocyanate and water, or by the employment of various gaseous blowing agents such as those of the hydrocarbon or halogenated hydrocarbon classes. The density is varied by the usual change in process limitations and proportions of the components used, as is well known in the art.

For the purpose of example, there will be listed below actual examples using different types of rigid and elastomeric polyurethane compositions. It will be understood that these examples are merely for the purpose of example and that the ranges of the components may be varied and that equivalents for the components may likewise be utilized, as is readily recognized in the art. Thus, it is well known that both rigid and elastomeric or flexible polyurethanes are old in the art and the examples listed below are merely exemplary.

In Example 1 below a medium density foam is employed in a single phase system.

EXAMPLE 1 10 pound density flexible foams Quadrol=N,N,NN-tetrakis (2 hydroxypropyl) ethylenediamine, OH-No. 768 145.0 Water:distilled water 3.4 TEA=tri ethyl amine (catalyst) 3.0 TMBD=N,N,N,N-tetramethyl 1,3 butane-diamine (catalyst) 10.0

7 DC200=silicone surfactant 3.0

B P-2000=2000 molecular weight diol (polypropylene glycol) Q. 524.40 Teracol 30=polyoxyethylated vegetable oil 58.20 Water=distilled water 2.08 TDI=toluene diisocyanate 227.00 Ratio: PP-111-B parts 100 FC-23 do 16 The flexible foam is employed by utilizing 100 parts of component B to 16 parts all by weight of component A. The resultant composition is then laid down in the crack to fill the crack or expansion joint completely up to A to /3" of the highway surface.

The slab sealer composition of Example 1 is shown in FIGURE 1 filling an expansion joint provided between abutting surface concrete pavement slabs and 12. A space 14 is provided at the top, such that the slab sealer 16 comes up only to within one-half inch to one-quarter inch of the top of the adjacent slabs 10 and 12. Thus, there is no protrusion or projection of the slab sealer that might tend to be scuffed or worn off.

In Examples 2 and 3 below a two phase system is employed using a low density rigid polyurethane foam as the bottom phase and a high density flexible polyurethane as the top phase.

EXAMPLE 2 4 pound density rigid foam A PEP-450 594.3 Blowing agent=trichloromonofluoromethane 121.9

TMBD=N,N,N,N-tetramethyl 1,3 butane-diamine (catalyst) .795 T12=dibutyl tin dilaurate (catalyst) .239

MDI=4,4-diphenylmethane diisocyanate 31.7

NCO 87.80

VC82=Viricol 82-a phosphorous containing polyol, OH-No.=2l2 10.37 DC-113=silicone surfactant 1.83

This polyurethane foam is made by mixing components A and B in the ratio of 72 parts by weight of component A to 100 parts by weight of component B. The joint is filled up to 1 /8 from the surface.

The so produced rigid 4 pound density foam is then covered with the pound elastomeric or flexible polyurethane system from Example 3 as follows:

This system is used to cover the low density rigid polyurethane foam of Example 2 system up to A" to of the highway surface.

Components A and B are mixed in the ratio of 100 parts by weight of component A to 14 parts of component B. This system is then employed to cover the 4 pound density foam up to A1" to /3" of the highway surface.

In the above example the low density polyurethane foam of Example 2 is laid down in an expansion joint shown in FIGURE 2 between slabs 20 and 22. The low density foam is laid down to the major portion of the depth of the expansion joint to form the lower part of the slab sealer indicated by the reference numeral 24. This can extend, as an example, in a joint of depth of 10" up to within about one and one-half inches of the top of the joint or crack. Subsequently, the liquid polyurethane composition forming the higher density flexible polyurethane foam from Example 3 is laid down, as indicated by the reference numeral 26, to within one-half inch or one-quarter inch of the top surface of the adjacent slabs 20 and 22. Thus, there is finally left a space 28 above the flexible polyurethane foam so that no protrusion of the slab sealer is presented above the pavement surfaces.

After the foam has set up it is then covered with the 15 pound density elastomeric system polyurethane foam described in Example 3. The elastomeric polyurethane composition is employed to fill the joint up to A to of the highway surface.

Various changes and modifications may be made Within this invention as will be readily understood by those skilled in the art. Thus, as an example, the invention is not limited to any particular polyurethane composition and various closed cell foams of the physical characteristics described may be employed where they present the same physical properties obtained and achieved through this invention. Various other changes and modifications will be readily apparent to those skilled in the art, and are included within the scope of this invention as defined by the claims appended hereto.

What is claimed is:

1. A slab sealer for concrete slabs spaced apart to provide a crack, said slab sealer being formed in situ in said crack and being comprised essentially of a rigid polyurethane of relatively low density bonded to the sides of said crack and filling the bottom of the crack and an elastomeric polyurethane of higher density than said rigid polyurethane bonded to the sides of said crack and to said rigid polyurethane and substantially filling the top of the crack to seal the same, the density of the rigid polyurethane foam being of about 2 to 10 pounds per cubic foot and the density of the elastomeric polyurethane being about 10 to 30 pounds per cubic foot.

2. A slab sealer for abutting concrete slabs spaced apart to provide a crack with the top surfaces of said slabs being in substantially the same plane, said slab sealer being formed in situ in said crack and being comprised essentially of a rigid polyurethane of relatively low density bonded to the sides of said crack and filling the bottom of the crack and an elastomeric polyurethane of higher density than said rigid polyurethane bonded to the sides of said crack and to said rigid polyurethane and substantially filling the top of the crack to seal the same,

said elastomeric polyurethane filling the top of said crack to just below the top surfaces of the slabs, the density of the rigid polyurethane foam being of about 2 to 10 pounds per cubic foot and the density of the elastomeric polyurethane being about 10 to 30 pounds per cubic foot.

3. A slab sealer for concrete slabs spaced apart to provide a crack, said slab sealer being formed in situ in said crack and being comprised essentially of a rigid polyurethane of relatively low density bonded to the sides of said crack and filling the bottom of the crack and an elastomeric polyurethane of higher density than said rigid polyurethane bonded to the sides of said crack and to said rigid polyurethane, and substantially filling the top of the crack to seal the same, the density of the rigid polyurethane foam being of about 2 to 10 pounds per cubic foot and the density of the elastomeric polyurethane being about 10 to 30 pounds per cubic foot, said rigid polyurethane being laid down in liquid form in a plurality of stages, and said elastomeric polyurethane likewise being laid down upon the top of the rigid polyurethane after it has solidified.

4. A slab sealer for concrete slabs spaced apart to provide a crack, said slab sealer being formed in situ in said crack and being comprised essentially of a rigid polyurethane of relatively low density bonded to the sides of said crack and filling the bottom of the crack and an elastomeric polyurethane of higher density than said rigid polyurethane bonded to the sides of said crack and to said rigid polyurethane and substantially filling the top of the crack to seal the same, the compressibility of the rigid polyurethane of relatively low density approximating the compressibility of the elastomeric polyurethane of higher density, the density of the rigid polyurethane foam being of about 2 to 10 pounds per cubic foot and the density of the elastomeric polyurethane being about 10 to 30 pounds per cubic foot.

5. A slab sealer for concrete slabs spaced apart to provide a crack, said slab sealer being formed in situ in said crack and being comprised essentially of a rigid polyurethane of relatively low density bonded to the sides of said crack and filling the bottom of the crack and an elastomeric polyurethane of higher density than said rigid polyurethane bonded to the sides of said crack and to said rigid polyurethane and substantially filling the top of the crack to seal the same, .the density of the rigid polyurethane foam being of about 2 to 10 pounds per cubic foot and the density of the elastomeric polyure thane being about 10 to 30 pounds per cubic foot, said rigid polyurethane being laid down in liquid form in a plurality of stages, and said elastomeric polyurethane likewise being laid down upon the top of the rigid polyurethane after it has solidified, the compressibility of the rigid polyurethane of relatively low density approximating the compressibility of the elastomeric polyurethane of higher density.

6. A slab sealer for concrete slabs spaced apart to provide a crack, said slab sealer being formed in situ in said crack and being comprised essentially of a rigid polyurethane of relatively low density bonded to the sides of said crack and filling the bottom of the crack and an elastomeric polyurethane of higher density than said rigid polyurethane bonded to the sides of said crack and to said rigid polyurethane and substantially filling the top of the crack to seal the same, the density of the elastomeric polyurethane being about 10 to 30 pounds per cubic foot.

7. A slab sealer for concrete slabs spaced apart to provide a crack, said slab sealer being formed in situ in said crack and being comprised essentially of a rigid polyurethane of relatively low density bonded to the sides of said crack and filling the bottom of the crack and an elastomeric polyurethane of higher density than said rigid polyurethane bonded to the sides of said crack and to said rigid polyurethane and substantially filling the top of the crack to seal the same, the density of the rigid polyurethane foam being of about 2 to 10 pounds per cubic foot and the density of the elastomeric polyurethane being about 10 to 30 pounds per cubic foot, said rigid polyurethane foam filling a major portion of thevdepth of the crack and the elastomeric polyurethane filling a minor portion.

References Cited UNITED STATES PATENTS 2,221,431 2,339,556 1/1944 Greenup et al. 94-182 3,111,069 11/1963 Farbish 94-18.2

JACOB L. NACKENOFF, Primary Examiner.

11/1940 Omansky 9418.2 

1. A SLAB SEALER FOR CONCRETE SLABS SPACED APART TO PROVIDE A CRACK, SAID SLAB SEALER BEING FORMED IN SITU IN SAID CRACK AND BEING COMPRISED ESSENTIALLY OF A RIGID POLYURETHANE OF RELATIVELY LOW DENSITY BONDED TO THE SIDES OF SAID CRACK AND FILLING THE BOTTOM OF THE CRACK AND AN ELASTOMERIC POLYURETHANE OF HIGHER DENSITY THAN SAID RIGID POLYURETHANE BONDED TO THE SIDES OF SAID CRACK AND TO SAID RIGID POLYURETHANE AND SUBSTANTIALLY FILLING THE TOP OF THE CRACK TO SEAL THE SAME, THE DENSITY OF THE RIGID POLYURETHANE FOAM BEING OF ABOUT 2 TO 10 POUNDS PER CUBIC FOOT AND THE DENSITY OF THE ELASTOMERIC POLYURETHANE BEING ABOUT 10 TO 30 POUNDS PER CUBIC FOOT. 